Using lens with a touchscreen, run HelloSanity. From the main screen, select "Effects". Select the back button. This returns you to the main screen. Repeat 3-4 times, and you will see the application exit.

It happens that the back button on the effects screen is in basically the same location as the quit button on the main screen. It appears that when the bug occurs, the "quit" button on the main screen is receiving a false/extra touch event (in the same location as the back button which was originally pressed) which causes the application to exit.